In the drilling, completions, production, transport, storage, and processing of crude oil and natural gas, including waste water associated with crude oil and gas production, and in the storage of residual fuel oil, contaminants are often encountered. Such contaminants may include, but are not necessarily limited to, hydrogen sulfide (H2S), mercaptans, and/or sulfides. The presence of H2S and mercaptans is extremely objectionable because they are an acute health hazard and often highly corrosive. Still another reason that mercaptans are undesirable is that they have highly noxious odors. The odors resulting from mercaptans are detectable by the human nose at comparatively low concentrations and are well known. For example, mercaptans are used to odorize natural gas and used as a repellant by skunks and other animals.
Further, other of these contaminants in hydrocarbon gas and/or mixed production systems may cause various health, safety and environmental (HSE) concerns and/or corrosion issues during the production, storage, transportation and processing of oil and gas.
To eliminate these contaminants and potentially harmful species, various scavenger systems have been developed in the art. However, many of these systems have limitations, including, but not necessarily limited to, low reactivity and therefore low efficiency, containing atypical components or elements that may adversely affect fuel or fluid quality, or may present toxicity concerns themselves and/or as the consequent reaction products.
It should be understood that nearly all scavenging systems for removing H2S, mercaptans and/or sulfides from oil-based systems such as crude oil, oil slurries, asphalt, and the like, cannot be assumed to work in mixed production systems or dry and/or wet hydrocarbon gas systems. “Mixed production systems” are defined herein to be predominantly water with some oil present, where the water is greater than about 50 wt % of the mixture, alternatively greater than about 60 wt % of the mixture, in another non-limiting embodiment greater than about 70 wt % of the mixture, in another non-restrictive version greater than about 80 wt % of the mixture, and still another alternative at least about 90 wt % of the mixture. In one non-limiting embodiment the amount of oil in a “mixed production system” may be up to about 10 wt %. A mixed production system may contain a hydrocarbon gas, such as natural gas. A “dry hydrocarbon gas system” is defined herein as a hydrocarbon gas produced from a subterranean formation having no more than about 7 lbs of water per mmscf (about 0.11 gr/m3), alternatively no greater than about 1 lb of water per mmscf (about 0.016 gr/m3), and in another non-limiting embodiment no greater than about 0.1 lbs of water per mmscf (about 0.0016 gr/m3). “Wet hydrocarbon gas” is defined as a hydrocarbon gas (e.g. natural gas) that contains more than 7 lbs of water/mmscf (0.11 gr/m3); in one non-limiting embodiment between about 50 independently to about 1,000 lbs water/mmscf (about 0.8 to about 16 gr/m3), alternatively less than 10,000 lbs water/mmscf (160 gr/m3). As defined herein “hydrocarbon” refers to naturally occurring hydrocarbons recovered from subterranean formations which are not necessarily limited to molecules having only hydrogen and carbon and which may include heteroatoms including, but not necessarily limited to oxygen, nitrogen, and sulfur.
In other words, it is not obvious or apparent that a scavenger that removes H2S, mercaptans and/or sulfides from oil-based systems will do so for a mixed production system and/or a dry hydrocarbon gas system and/or a wet hydrocarbon gas system. Nearly all scavengers that work well for oil-based systems do not work, or do not work very well or very effectively for mixed production systems but might work for dry hydrocarbon gas systems and/or a wet hydrocarbon gas system; such scavengers include, and are not necessarily limited to, glyoxal, triazines and other amines. Many conventional H2S scavengers such as triazine work poorly in mixed production systems where the water content is above 20%. In addition to low effectiveness of these scavengers in mixed production systems the scaling and/or solid formation issues are often encountered.
Acrolein is the one well-known scavenger that is effective at scavenging H2S, mercaptans and/or sulfides from oil-based systems as well as from a mixed production system, but acrolein is also well known to be very hazardous to handle and work with.
It would be desirable if methods and/or compositions could be devised that would, reduce, eliminate, take out or otherwise remove such contaminants from these mixed production and/or dry hydrocarbon gas systems, as well as reduce, alleviate or eliminate corrosion caused by these undesired contaminants.